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What is the minimum diameter requirement for pressure-building drains according to the Illinois Plumbing Code?

  1. 1 inch

  2. 2 inches

  3. 3 inches

  4. 4 inches

The correct answer is: 2 inches

The Illinois Plumbing Code specifies that the minimum diameter for pressure-building drains must be 2 inches. This requirement ensures that the drain system has adequate capacity to handle the expected flow and pressure conditions, which is critical for maintaining proper drainage and preventing backflow or overloading of the plumbing system. A diameter of 2 inches strikes a balance between providing sufficient capacity without being overly large, which could increase the risk of stagnation if not properly utilized. Following this requirement is essential for ensuring efficiency and reliability in plumbing systems. Other choices suggest larger or smaller diameters, which do not meet the specific needs outlined by the code.